The major objective of this study will be to correlate the process of aging with CNS homeostatic malfunction either attributed to and/or mediated by changes in brain oxidative metabolism and microvascular alterations. We will test the hypotheses: (1) that a decline in the rate and/or efficiency of state 3 respiration occurs with age which may be attributed to altered respiratory chain function; and (2) that the declining capacity of aged brain to sustain normal CNS function is a reflection of altered microvascular control. Our studies will confront these two challenges directly. In vivo noninvasive optical monitoring techniques will be used to continuously measure changes in brain activity oxidative metabolism and circulatory parameters. These functional changes will be directly compared with in vitro measured changes in CNS metabolite concentrations. The data will be correlated with age under steady state or "resting" conditions and during electrical, physiological and pharmacological induced stress mediated states of altered brain function.